Hard Constraints for Prioritized Objective.pdf

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1、HardConstraintsforPrioritizedObjectiveNonlinearMPCChristopherE.LongandEdwardP.GatzkeUniversityofSouthCarolina,DepartmentofChemicalEngineering,Columbia,SC,USA29208gatzke@sc.eduSummary.ThispaperpresentsaNonlinearModelPredictiveControl(NMPC)al-gorithmth

2、atuseshardvariableconstraintstoallowforcontrolobjectiveprioritiza-tion.Traditionalprioritizedobjectiveapproachescanrequirethesolutionofacomplexmixed-integerprogram.Theformulationpresentedinthisworkreliesonthefeasibil-ityandsolutionofarelativelysmalll

3、ogicalsequenceofpurelycontinuousnonlinearprograms(NLP).Theproposedsolutionmethodforaccomodationofdiscretecontrolobjectivesisequivalenttosolutionoftheoverallmixed-integernonlinearprogrammingproblem.Theperformanceofthealgorithmisdemonstratedonasimulate

4、dmultivari-ablenetworkofairpressuretanks.1IntroductionModelPredictiveControl(MPC)technologyismostnotableforitsabilitytocon-trolcomplexmultivariableindustrialsystems.Themodel-basedcontrolschemereliesontheonlinesolutionofanoptimizationproblemfortheopti

5、malcon-trolsequencethatminimizesacostfunctionwhichevaluatesthesystemoversomepredictionhorizon.Thetypicalcostfunctionaccountsfornumerouscon-trolobjectivesspanningdifferentlevelsofrelativeimportanceincludingthosestemmingfromequipmentlimitsandsafetyconce

6、rns,productqualityspecifica-tions,aswellaseconomicgoals.Traditionalformulationspenalizeviolationsofsoftconstraintstoachievethedesiredperformance.However,theyoftenrelyonadhoctuningtodeterminetheappropriatetrade-offbetweenthevariouscontrolobjectives.More

7、over,thetuningbecomeslessintuitiveforsystemsofincreasingcomplexity.Recentstudieshavefocusedonensuringthatcontrolobjectiveprioritizationishandledeffectively[3,4,7,8,13,14,18,19].Mixedintegermethodsutilizepropositionallogic[17]andbinaryvariablestodefinew

8、hetherdiscretecontrolobjectiveshavebeenmetandwhethertheyaremetinorderofpriority.Termsareincludedinthecostfunctiontopenalizefailuretomeettheprioritizedob-jectivesandtheresultingmixedintegerprogramissolvedtodeterminetheappropriateinputmove(s).Neverthel